A wealth of habitable planets in the Milky Way

Jan 11, 2012
There are 100 billion stars in the Milky Way. Observations show that planets orbiting around stars are more the rule than the exception and approximately one out of every ten stars have a planet roughly the size of the Earth with an orbit that, if there was water and atmosphere, would create a temperature and climate roughly that same as on Earth -- we could live there. Credit: ESO/M. Kornmesser

An international team has used the technique of gravitational microlensing to measure how common planets are in the Milky Way.

Six years of observations of millions of now show how common it is for stars to have in orbits around them. Using a method that is highly sensitive to planets that lie in a around the host stars, astronomers, including members from the Niels Bohr Institute, have discovered that most of the Milky Way's 100 billion stars have planets that are very similar to the Earth-like planets in our own solar system – Mercury, Venus, Earth and Mars, while planets like Jupiter and Saturn are more rare. The results are published in the prestigious scientific journal, Nature.

"Our results show that planets orbiting around stars are more the rule than the exception. In a typical solar system approximately four planets have their orbits in the terrestrial zone, which is the distance from the star where you can find solid planets. On average, there are 1.6 planets in the area around the stars that corresponds to the area between Venus and Saturn" explains astronomer Uffe Gråe Jørgensen, head of the research group Astrophysics and Planetary Science at the Niels Bohr Institute at the University of Copenhagen.

Searching for exoplanets

Over 1000 exoplanets have been found in our galaxy, the , and most have been found using either the radial velocity method or the transit method, both of which are best suited to be able to find planets that are large and relatively close to their host star. With the radial velocity method you can measure that a star rocks in small circular motions due to a revolving planet's gravitational force. With the transit method you measure periodic changes in the brightness of a star. When a planet moves in front of the star, there is a little dip in the star's brightness and if this little dip occurs regularly, further observations can reveal whether there it is a planet. With both methods you most often find large planets in such small orbits around their stars, that they have no equivalents in our own solar system.

Habitable exoplanets

In order to find planets similar to the planets we know from our own solar system, researchers must use a third method – gravitational microlensing observations. But the method requires very special conditions concerning the stars location in the galaxy.

Uffe Gråe Jørgensen explains that you need to have two stars that lie on a straight line in relation to us here on Earth. Then the light from the background star is amplified by the gravity of the foreground star, which thus acts as a magnifying glass. When the stars pass close by each other in the sky, astronomers can observe the light from the background star first increase and then decrease again. If there is a planet around the foreground star, there might be a little extra bump on the light curve. But if the planet is very close to the star, the bump 'drowns' on the light curve, and if the planet is very far from star, you do not see it. "Therefore the method is most sensitive to planets that lie at an Earth-like distance from a star," explains Uffe Gråe Jørgensen.

It is rare that two planets pass by each other closely enough to create a microlens. We have therefore implemented a strategic search on two levels. Every starry night the research group scans 100 million stars using telescopes in Chile and New Zealand. If the scanning identifies a stellar location with a possible microlensing effect, it is automatically registered and all researchers are notified. Then the best 'lenses' are observed more closely at high resolution and their light curves are analysed. One of the places this is done is at the Danish 1.5 meter telescope at ESO's La Silla Observatory in Chile.

"In a six year period from 2002 to 2007, we observed 500 stars at high resolution. In 10 of the stars we directly see the lens effect of a planet, and for the others we could use statistical arguments to determine how many planets the stars had on average. To be exact, we found that the zone that corresponds to the area between Venus and Saturn in our solar system had and average of 1.6 planets the size of five Earth masses or more," explains Uffe Gråe Jørgensen.

Billions of habitable planets

The microlensing results complement the best existing transit and radial velocity measurements. Using transit measurements, the American Kepler satellite has identified a very large number of relatively small planets in orbits smaller than even the innermost planet in our own solar system, Mercury, while many years of radial velocity measurements have revealed a large number of very large planets in both very small orbits and slightly larger orbits.

"Our microlensing data complements the other two methods by identifying small and large planets in the area midway between the transit and radial velocity measurements. Together, the three methods are, for the first time, able to say something about how common our own solar system is, as well as how many stars appear to have Earth-size planets in the orbital area where liquid what could, in principle, exist as lakes, rivers and oceans – that is to say, where life as we know it from Earth could exist in principle," says Uffe Gråe Jørgensen.

He explains that a statistical analysis of all three methods combined shows that out of the Milky Way's 100 billion stars, there are about 10 billion stars with planets in the habitable zone. This means that there may be billions of habitable planets in the Milky Way. For thousands of years people have been guessing how many planets there might be out there among the stars, where we could, in principle at least, live. Today we know this.

Are we alone in the universe?

But it is one thing, that the planets have the right temperature to be habitable in principle, but quite another thing, whether they are inhabited – whether there is life and perhaps even intelligent life on the planets.

"There are so many unique events in our that have created the basis for the development of life on Earth. Comets brought water to our planet so that life could arise and a series of random events set in motion an evolution that lead to humans and intelligent life. It is very unlikely that the same circumstances would be present in other solar systems," believes Uffe Gråe Jørgensen, "but perhaps other coincidences in other solar systems have led to entirely different and exciting new forms of life. Recent research of planets around other stars has shown us that there is in any case billions of planets with orbits like Earth and of comparable size to the Earth."

Explore further: Astronomer confirms a new "Super-Earth" planet

Provided by University of Copenhagen

4.8 /5 (29 votes)

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droid001
5 / 5 (13) Jan 11, 2012
"Billions of habitable planets. Are we alone in the universe?"
Something wrong with this picture.
Xbw
1.9 / 5 (37) Jan 11, 2012
It is almost statistically impossible to rule out other planets with liquid water. 10 billion systems means that even if 1% of those systems have planets with liquid water, that is 10 million planets and 1% of those planets have life, that is 100,000 planets with life, and if even 1% of those life filled planets have intelligent life, that's 1000 different varieties of intelligent life. Not bad odds considering 1% is a rather low estimate.
dogbert
1.7 / 5 (39) Jan 11, 2012
Even planets of earthlike size and position to sun like stars with water and atmosphere need not be habitable. Unless there is life on such planets, the atmosphere is unlikely to contain free oxygen in sufficient concentration to support us. And we have no indication at all that life exists anywhere but this solar system.

I would like for life to be abundant in this galaxy, but we have no reason to suspect that it is.
Deathclock
3.6 / 5 (33) Jan 11, 2012
I would like for life to be abundant in this galaxy, but we have no reason to suspect that it is.


We have no reason to believe it is rare either. We know life ccurred at least once, and we strongly suspect that physical laws are universal, which leads to homogeneity.
zbarlici
5 / 5 (7) Jan 11, 2012
Is it possible to study the formation of star systems in their infancy(before planets actually form) to find out if it is more common than not for the elements in the dust to organize in such a manner that would ultimately give birth to a star system such as our own(with habitable planets)?.
zbarlici
5 / 5 (7) Jan 11, 2012
that way we could have another tool in our arsenal to say whether star fromation with habitable planets is either commonplace or the exeption...
Vendicar_Decarian
3.5 / 5 (20) Jan 12, 2012
"10 billion systems means that even if 1% of those systems have planets with liquid water, that is 10 million planets" - xbw

Division by 100 is simple. Watch...

10 billion/10 = 1 billion
1 billion/10 = 100 million.

"that's 1000 different varieties of intelligent life" - xbw

10,000

Thank you for your time.
zbarlici
4.4 / 5 (8) Jan 12, 2012
methinks it`s not as straightforward as that... i imagine stars that are not in the outer spiral arms of the galaxy are a lot less likely to host habitable planets due to interfering forces from nearby stars/phenomenae
Sinister1811
1.9 / 5 (14) Jan 12, 2012
Damn it, when are they going to discover a way to travel to these star systems, so we can see whether or not these planets *are* habitable. It would be awesome to know so much more about them etc.

For example; They might not have suitable atmospheric pressures, stronger/weaker gravity, lack magnetic fields, ozone layer, no moon, stronger tides etc. They might even be in the habitable zone but lack a trace of liquid water. How would we know, unless we see them for ourselves?
Smarrelli
4.5 / 5 (4) Jan 12, 2012
Vendicar, you wouldn't happen to be confusing '1' for '10' are you? 1% of 10 billion is surely 100,000,000 (one hundred million). If you were assuming 10%, your numbers are correct; if you weren't assuming 10% then perhaps your finger slipped in your calculations, each one of them.
hagger
3.4 / 5 (9) Jan 12, 2012
it's human arrogance to presume we are the only one out here..it is impossible for there to be no other life..religion is to blame for this too..we are not alone..the universe does not know we are even here..only we know that..to look up into millions of light years of space and say we are the only one's shows ignorance, arrogance, and an ego so large i am suprised the planet is big enough to hold you...if you sow a field of corn..other growth constructs are available...would you expect only one ear of corn to grow..dream on...drop the narrow arrogance and the ego...we are not unique or special..thses are human terms only..one good sized rock and we are nothing but star dust..and nobody would be the wiser...esp the universe...
dogbert
1.5 / 5 (45) Jan 12, 2012
hagger,
it's human arrogance to presume we are the only one out here..it is impossible for there to be no other life..religion is to blame for this too..we are not alone


Nothing to do with arrogance or religion. There is simply no indication at all that life exists anywhere but here.

You cannot rationally assign a positive probability when there are zero known instances outside this solar system. An assertion of certainty has no rationality.
Sinister1811
2.8 / 5 (18) Jan 12, 2012
The good news is that if there's a wealth of habitable planets out there, there's probably a wealth of habitable moons as well.
antialias_physorg
4.3 / 5 (12) Jan 12, 2012
I think it's important to make the distinction between 'habitable' and 'human compatible'. The former merely means that life could develop there similarly to theway it has here on Earth - because there is an ample energy source and the type of chemistry we have here has a chance to function (water in different states, not too cold so that chemical reactions can occur at a reasonable rate, etc. )

So 'habitable' is a set that is a LOT larger than 'human compatible'.

I'd wager that the likelyhood that we find a planet that has the right

- oxygen/nitrogen balance
- radiation level
- gravity
- atmospheric density
- lack of poisonous gases
- etc.
to support human life without a full life support suit is so remote as to be astronomically small*

* Although - to be fair - we're dealing with an astronomically large search space.
Paljor
4.6 / 5 (5) Jan 12, 2012
Well do not forget, whats deadly/toxic to us or earth life may not be deadly/toxic to other forms of life
antialias_physorg
4.8 / 5 (11) Jan 12, 2012
Well do not forget, whats deadly/toxic to us or earth life may not be deadly/toxic to other forms of life


You don't even have togo extraterrestrial to have proof of that.

Oxygen is a deadly toxin to all that life which created it on Earth. The oxygen we breathe is the WASTE produced by billions of years of bacteria doing their thing in anaerobic conditions. An oxygen/nitrogen atmosphere is probably not to be found on a lifeless planet. So we shouldn't expect to find any holiday-planets for humans anywhere.

Carbon dioxide is pretty poisonous to us, too, in any but trace amounts. Earth plants, on the other hand, thrive in high carbon dioxide conditions.
Xbw
1.4 / 5 (32) Jan 12, 2012
"10 billion systems means that even if 1% of those systems have planets with liquid water, that is 10 million planets" - xbw

Division by 100 is simple. Watch...

10 billion/10 = 1 billion
1 billion/10 = 100 million.

"that's 1000 different varieties of intelligent life" - xbw

10,000

Thank you for your time.

haha Vendicar you moron. Learn math. Here let me make it easy for you. 1,000,000,000 x .01 (.01 means 1% by the way) = 10,000,000
I was factoring from 1 billion. However, if I had gone off 10, then yes, 10,000 planets which only goes to strengthen my case.

I graduated math!
Xbw
1.4 / 5 (33) Jan 12, 2012
Oh and yes I meant to say 1 billion. My math was correct however :)
Deathclock
3.4 / 5 (23) Jan 12, 2012
No, you said:

"10 billion systems means that even if 1% of those systems have planets with liquid water, that is 10 million planets" - xbw"

It is 100 million, not 10 million. Just admit you made a simple mistake that everyone makes sometimes, Jesus...
Deathclock
3.5 / 5 (22) Jan 12, 2012
Oh and yes I meant to say 1 billion. My math was correct however :)


I don't know why you would say either, since the article mentions 100 billion stars in the milky way, where did 10 billion or 1 billion come from?
Xbw
1.2 / 5 (33) Jan 12, 2012
He explains that a statistical analysis of all three methods combined shows that out of the Milky Way's 100 billion stars, there are about 10 billion stars with planets in the habitable zone.

That. Although I scaled that number down to 1 billion.
Deathclock
1.7 / 5 (11) Jan 12, 2012
Oh okay, sorry.
Xbw
1.4 / 5 (28) Jan 12, 2012
Oh okay, sorry.

No prob although I should have said 1 billion in my initial estimate since it was based of that. My bad.
TheGhostofOtto1923
3.3 / 5 (14) Jan 12, 2012
And we have no indication at all that life exists anywhere but this solar system.
No indication YET. Without the 'yet' word people are tempted to conclude 'never' and 'so why look?'
I would like for life to be abundant in this galaxy, but we have no reason to suspect that it is.
We have MANY reasons to suspect that life exists elsewhere, and are finding more reasons constantly. This article cites new reasons to suspect that life exists elsewhere.
Modernmystic
1.5 / 5 (30) Jan 12, 2012
We have no reason to believe it is rare either. We know life ccurred at least once, and we strongly suspect that physical laws are universal, which leads to homogeneity.


The problem is we don't have any idea how homogenous a given planet has to be in order to support complex, intelligent, technological life. We may very well be the only example in the entire universe despite the isotropy we see out there...
dogbert
1.7 / 5 (30) Jan 12, 2012
No, Otto, we have no indication of life anywhere except in this solar system.

Life may be abundant or it may be extremely rare, but based on our lack of any evidence of life anywhere except here, we have absolutely no reason to assign a probability that life exists outside of this solar system.
Vendicar_Decarian
3.9 / 5 (11) Jan 12, 2012

"10 billion systems means that even if 1% of those systems have planets with liquid water, that is 10 million planets" - xbw

"I was factoring from 1 billion." - xbw

No. You were factoring for 10 billion, as you so clearly state in your opening sentence.
LowIQ
5 / 5 (8) Jan 12, 2012
Out there - galaxies every where we look, stars every where we look, planetary systems everywhere we look, organic compounds everywhere we look.

On earth life everywhere we look.

Personally I feel there are damn good reasons to be more than a little optimistic that planets on which life (generic term not earth originated/adapted) can evolve and thrive are out there, and in vast numbers.
Vendicar_Decarian
4.2 / 5 (19) Jan 12, 2012
"we have absolutely no reason to assign a probability that life exists outside of this solar system." - dogberTard

Correction, we have no statistical reason for doing so.

We can still estimate based on experience, expectation, modeling, deduction and induction etc.

Vendicar_Decarian
4.3 / 5 (16) Jan 12, 2012
Within the next decade we will have a good estimate of the number of earth like planets in our galaxy and will have even measured the basic atmospheric composition of a few of those planets.

Direct spectroscopy of those planetary atmospheres will have to wait for the launch of an interfrometric spectrograph.

Xbw
1.5 / 5 (28) Jan 12, 2012
And travel to any of those planets will have to wait for major improvement to propulsion. We will have to devise some way to go outside the laws of physics since a trip at even 99% the speed of light will take hundreds if not thousands of years. Not to mention, the theory that the closer you get to the speed of light, the slower time moves for you.
TheGhostofOtto1923
2.5 / 5 (11) Jan 12, 2012
No, Otto, we have no indication of life anywhere except in this solar system.

Life may be abundant or it may be extremely rare, but based on our lack of any evidence of life anywhere except here, we have absolutely no reason to assign a probability that life exists outside of this solar system.
Hmmm. Lets do a little research shall we?

"Probability is ordinarily used to describe an attitude of mind towards some proposition of whose truth we are not certain."

-In other words we can have an attitude about the possibility of life without necessarily having direct evidence. Yes?

We DO have examples of it here. Even if we were to find it elsewhere, according to your logic this would not mean we would find it anywhere else.

But since we DO have it here we can consider this 'reason to suspect' that we might find it elsewhere under similar conditions.

"Suspect (verb) Have an idea or impression of the existence, presence, or truth of (something) without certain proof."

-YOUR words.
TheGhostofOtto1923
2.5 / 5 (11) Jan 12, 2012
@x
Let me point out (3) major errors in your post:
We will have to devise some way to go outside the laws of physics
Any way we devise to do it will be firmly within the laws of physics.
since a trip at even 99% the speed of light will take hundreds if not thousands of years.
A trip to the nearest star at 10% lightspeed will take some 40 years.
Not to mention, the theory that the closer you get to the speed of light, the slower time moves for you.
No you would experience LESS time passed than an observer back home.

Might I suggest a resource?
https://www.googl...ie=UTF-8

-See frank, this is the level of acumen I was referring to.
antialias_physorg
4 / 5 (8) Jan 12, 2012
organic compounds everywhere we look.

"Organic" just means "carbon based".
That we know that carbon exists elsewhere is no indication of life.

I'm with dogbert on this one: We have no basis for assigning a probability either way. So statements like "there is likely life out there" are insupportable (as is the opposite statement!)

All we can have is an attitude (e.g. hopeful for life out there or not) - but that's just personal gut feeling.
LowIQ
4.6 / 5 (5) Jan 12, 2012

"Organic" just means "carbon based".
That we know that carbon exists elsewhere is no indication of life.

What I was alluding to is the fact that carbon compounds, not carbon, as found in life on earth appear to be extremely common even in deepspace and this lends weight to the argument that it is highly probable that other carbon based life exists out there as for non carbon based then we cannot say.

It is perfectly acceptable based on the astronomical data and knowledge of bio/organic science to assign a probability to finding non terrestrial life and would argue that the balance tips in favour of this being true rather than the 50:50 stance which would have been valid without the above mentioned knowledge.
Modernmystic
1.4 / 5 (27) Jan 13, 2012
It is perfectly acceptable based on the astronomical data and knowledge of bio/organic science to assign a probability to finding non terrestrial life and would argue that the balance tips in favour of this being true rather than the 50:50 stance which would have been valid without the above mentioned knowledge.


This would be true, but for one problem. We have no satisfactory theory about bio-genesis. Without it we simply can't rationally assign probabilities about life elsewhere in the universe.

My GUT feeling, based on observation, is that simple life is probably quite common, complex life is rare, complex intelligent life is exceedingly rare, and complex intelligent technological life may not exist anywhere but here.
LowIQ
5 / 5 (3) Jan 13, 2012
"This would be true, but for one problem. We have no satisfactory theory about bio-genesis. Without it we simply can't rationally assign probabilities about life elsewhere in the universe."

I totally agree on the issue of biogenesis - but we do have theories. Those theories together with other data such as the abundance of galaxies, stars etc and our knowledge of how current DNA based life on earth evolved from the first simple replicating molecule, however incomplete, does allow science to take an educated guess and with each new piece of the puzzle the scales tip further and further out of balance in favour there being something out there.

The search for exoplanets is a prime example based on a sample size of one and our modeling of solar system/planetary formation the probability of other stars having planetary systems was high enough to initiate a search and look what we've found.

Theres more chance of finding simple ET life than me winning the lotto :-)

LowIQ
4.3 / 5 (4) Jan 13, 2012
Also I'm not sure a theory of biogenesis would help as 'life' whatever that is could possibly arise in a huge number of ways i.e. in terms of the conditions that are conducive to the formation of simple replicators that are subject to darwinian evolution.

Even if scientists on earth recreate DNA based life from a primordial soup in a lab somewhere that still wouldn't mean that we'd cracked how life first started on earth.

Deathclock
2.3 / 5 (12) Jan 13, 2012
Even if scientists on earth recreate DNA based life from a primordial soup in a lab somewhere that still wouldn't mean that we'd cracked how life first started on earth.


Sure, but it is fundamentally impossible to prove anything. The slim possibility always exists that our collective perception of reality is entirely illusory. Science is not in the business of proofs. Mathematicians concern themselves with proofs, but that which is proven is only proven relative to a given context. Scientists could also prove things relative to a given context, known as first principles, or axioms, but that is not the point of the application of the scientific method.
Modernmystic
1.2 / 5 (27) Jan 14, 2012
Sure, but it is fundamentally impossible to prove anything. The slim possibility always exists that our collective perception of reality is entirely illusory.


Hence faith...even in scientific circles. Without it there is no motivation, no meaning. If scientists didn't at least at some level BELIEVE reality is real then why bother with "proving" anything? We may be a simulation, or a simulation of a simulation of a....you get the point. Even if true the only course of action open is to act "as if" what we perceive is indeed real...imo....
Deathclock
2.3 / 5 (12) Jan 14, 2012
Sure, but it is fundamentally impossible to prove anything. The slim possibility always exists that our collective perception of reality is entirely illusory.


Hence faith...even in scientific circles.


Faith is belief without evidence, not belief without proof. Faith should be avoided, it is inherently illogical. Evidence certainly does exist, so if you have evidence for something and you believe it to be true that is not faith, that is evidence backed logical belief.
dogbert
1.1 / 5 (29) Jan 14, 2012
Faith is belief without evidence, not belief without proof. Faith should be avoided, it is inherently illogical.


No, faith is belief based on evidence.

Belief without evidence is indeed foolish. Such faith is sometimes called 'blind faith'.

Since there is no evidence that life exists anywhere except our solar system, belief that there is life outside this solar system falls in the category of blind faith.
Deathclock
2.2 / 5 (12) Jan 14, 2012
Faith is belief without evidence, not belief without proof. Faith should be avoided, it is inherently illogical.


No, faith is belief based on evidence.


ROFL

No, faith means unconditional belief, or belief with, without, or even despite evidence. Faith is a subset of belief that indicates your devotion, logical or otherwise, to the belief in question. Basically faith means that you belief in something regardless of the evidence.

Faith is always irrational. It is irrational to believe in something regardless of the evidence in favor of or against it.
Modernmystic
1.2 / 5 (24) Jan 14, 2012

Evidence certainly does exist, so if you have evidence for something and you believe it to be true that is not faith, that is evidence backed logical belief.


Evidence based on what? What your brain tells you? Is that real? It's electrical signals interpreted by an organ. We're told it's an organ based on electrical signals interpreted by what we THINK are simply a collection of the same organs in what we believe are other people's heads. How do you KNOW it's real? From an epistemological standpoint we're ALL believers.
dogbert
1.2 / 5 (18) Jan 14, 2012
Deathclock,

You redefine faith to mean stupid, then exhibit such faith in extrasolar life:

ROFL if you want. Stupid often does that. Here is your blind faith statement:
Evidence certainly does exist, so if you have evidence for something and you believe it to be true that is not faith, that is evidence backed logical belief.


You have blind faith since there is absolutely no evidence of extrasolar life.

Henrik
1.4 / 5 (21) Jan 14, 2012
Proof is a tricky concept. Science can never conclusively prove anything, but just make it very plausible. The reason is that science is ultimately based on faith. Faith that our memory can be trusted, and our senses are reliable. Faith that the laws of nature are uniform and our logical thinking is truthful. Faith that the world is real and our observations are not illusory. We cannot prove all of that, we just assume they are true. Like Einstein said, science without faith is lame. Scientists may think otherwise, but they have conveniently forgotten that they are standing on the shoulders of faith.
Henrik
1.6 / 5 (21) Jan 14, 2012
Faith is always irrational


That statement is a logical fallacy. The definition of faith is a belief in something for which there is no conclusive proof. But that doesn't make it irrational! Faith would only be irrational if there is only overwhelming evidence against its presuppositions. But in most cases faith is based on actual evidence. For instance, if someone boards a plane he believes that the pilot is competent to fly it safely to the destination. There is enough evidence to warrant such a belief, but no conclusive proof. Flying is therefore based on a completely rational faith in the safety of air travel.
Modernmystic
1.2 / 5 (25) Jan 14, 2012
FTA

He explains that a statistical analysis of all three methods combined shows that out of the Milky Way's 100 billion stars, there are about 10 billion stars with planets in the habitable zone.


And how many of these are within the GHC? Have plate tectonics? A magnetic field? A large natural satellite? Sufficient axial tilt? High enough metalicity? Etc etc ect...
Egleton
1.9 / 5 (7) Jan 15, 2012
Once we are out of the gravity well I can think of no good reason to go back down.
Other technologically advanced civilisations would come to the same conclusion.
Their vast habitats would be insignificant on a cosmic scale.
http://www.youtub...=related
WhiteJim
2.2 / 5 (9) Jan 15, 2012
It is best to believe that life and inteligent life exists everywhere in the universe and that we have only to find it.

To believe we are alone in the univese is stupid and places us in the dark ages.

There can be no harm if we believe we are not alone and it turns out we are.

There is a great deal of harm done if we believe we are alone and it turns out we are not.
MorituriMax
1.8 / 5 (5) Jan 15, 2012
"A Wealth" implies value we can get to, planets in other star systems are way beyond our reach. Thus, no value. The title would have been better as

"A buttload of planets in the Milky Way."

I removed "habitable" since we have no way to know how many of them would actually be habitable.
Deathclock
2.2 / 5 (12) Jan 15, 2012
Deathclock,

You redefine faith to mean stupid, then exhibit such faith in extrasolar life:

ROFL if you want. Stupid often does that. Here is your blind faith statement:
Evidence certainly does exist, so if you have evidence for something and you believe it to be true that is not faith, that is evidence backed logical belief.


You have blind faith since there is absolutely no evidence of extrasolar life.



What the hell are you talking about? I never said that I believe in life on other planets.

I believe that there COULD BE... but there is not enough evidence to believe that there IS.

Stop making things up to suit your argument (or ad hom attack, whatever).
Mayday
2.6 / 5 (7) Jan 15, 2012
It is also worth remembering that there have been many countless branches on our Earth-bound tree of life, yet after billions of years, only one has managed to lead to a civilization-building intelligent species. I am not qualified to do the math that would reveal the likelihood of another duplicate Earth repeating that accomplishment. Much to my chagrin, I find it quite likely that advanced, space-faring intelligent societies are probably extremely, extremely rare. And I agree with Hawking that if they are successfully moving through the galaxy, then they are probably very aggressive in their tactics in order to cut their risks and losses.
Deathclock
2.1 / 5 (11) Jan 15, 2012
Oh and I did not redefine faith to mean anything.

Faith means unconditional belief, which includes belief absent of or even despite of evidence.

You never have to have faith in anything, nor should you. Faith is a weakness, it is inherently illogical.
dogbert
1.2 / 5 (20) Jan 15, 2012
Faith means unconditional belief, which includes belief absent of or even despite of evidence.

You never have to have faith in anything, nor should you. Faith is a weakness, it is inherently illogical.


You must be very lonely, since you cannot have faith in anyone. And you are wrong in redefining faith to mean 'blind faith'. Faith is generally based on evidence.
Skultch
4 / 5 (4) Jan 15, 2012
The dictionary.com definition of faith is "belief that is not based on proof." Dogbert is correct. However, a significant percentage of the "faithful" use it differently; just as Deathclock used it. I urge the Physorg community to establish working definitions of this word (and some others) before commencing a debate that hinges on the subtle differences in usage.
Skultch
5 / 5 (4) Jan 15, 2012
That said, and for example, IMHO there is more evidence to suggest life exists elsewhere in the Milky Way, than there is evidence to support an interventionist creator (the most common form of faith). I think that may be the real difference in opinion here. I would be pleased to see this thread NOT go on about trying to "prove" one of these opinions, but argue the probabilities of the two positions instead.
Deathclock
2.2 / 5 (12) Jan 15, 2012
The dictionary.com definition of faith is "belief that is not based on proof." Dogbert is correct. However, a significant percentage of the "faithful" use it differently; just as Deathclock used it. I urge the Physorg community to establish working definitions of this word (and some others) before commencing a debate that hinges on the subtle differences in usage.


Dictionaries are almost always insufficient when discussing philosophy. The reason the dictionary definition is insufficient in this case is that there is no such thing as "proof". You cannot prove anything to be true, because regardless of the efforts you go to and the evidence you have there is always the slim possibility that our perception of reality is completely illusory.

"Proof" is an anti-concept. Evidence is what matters. Faith defined as belief without proof is meaningless, nothing has proof, nothing is ever proven unless that proof is relative to a given context, defined by axioms.
TheGhostofOtto1923
2.5 / 5 (11) Jan 15, 2012
You must be very lonely, since you cannot have faith in anyone. And you are wrong in redefining faith to mean 'blind faith'.
Thinly-veiled ad hom doggy doo. I would say you're lonely enough to need to adopt an imaginary sky fairy to talk to. Why don't you just get a dog?
Faith is generally based on evidence.
??? Since there is NO evidence for your adopted sky fairy whatsoever, and a great deal of evidence AGAINST it, what is YOUR faith based upon exactly? The need to have an imaginary sky fairy to talk to?

Or is it fear of death? 'The Valley of the Shadow...' Fear and loneliness can be very tangible things but they still do not make your superstitious palliatives any more real.
Skultch
5 / 5 (3) Jan 15, 2012
Agreed, but that is your point, and you have yet to acknowledge mine. Not establishing and agreeing upon a common definition almost always results in an argument being a complete waste of time. Your choice of words suggests you don't care what def MM uses, as long as you are "right." If true, this is a mistake. If false, my apologies. Physorg is replete with posters talking past each other and making no progress in learning. This is exactly what you and MM are currently doing. Shit, I think I've done the same with MM. Be careful with people who don't want a common understanding, but merely want their opinion published. They will waste your time.
Deathclock
2.5 / 5 (13) Jan 15, 2012
Not establishing and agreeing upon a common definition almost always results in an argument being a complete waste of time. Physorg is replete with posters talking past each other and making no progress in learning. This is exactly what you and MM are currently doing. Shit, I think I've done the same with MM. Be careful with people who don't want a common understanding, but merely want their opinion published. They will waste your time.


Sure, yes I agree.

The question is then if others can agree that the most reasonable definition of faith is "unconditional belief" since, as I have shown, the definition given by the dictionary is useless.

As an aside, these shortcomings of common dictionaries is more often the rule than the exception when dealing with matters of science, logic, and philosophy. "Proof" as a concept is useful in informal discourse but utterly useless when it is meant to be taken literally.
Skultch
5 / 5 (3) Jan 15, 2012
So, MM, since we can't really live in a world where nothing is more certain than anything else, how would you compare the certainty of the existence of an interventionist god (most common form of faith) and the newly discovered level of certainty that life exists on extrasolar planets?
dogbert
1.3 / 5 (16) Jan 15, 2012
TheGhostofOtto1923,
Always have to interject religion into every discussion, don't you?

This discussion is about extrasolar life. It is not about religion.
jaftec
3 / 5 (3) Jan 15, 2012
First off regarding the probabilty of other planets in our galaxy supporting life i think we should simplify the argument a bit down to purely observational. I think sometimes you get so caught up in the math or scienc, you lose your common sense. walk out of your house at night and look up at the sky and observe the countless amounts of stars beaming light down at you. our sun is a star. our sun has a bunch of planets spinning around it. what makes any of you think those stars (or "suns" to those that may live there) above your head in the night sky dont have the same company we do? Forget faith forget science forget math for a second and just use common sense.
antialias_physorg
3.2 / 5 (6) Jan 16, 2012
yet after billions of years, only one has managed to lead to a civilization-building intelligent species.

Only one that we know of. We barely find remnants of human activity 100000 years old. If there had been a 'dinosaur civilization' or somesuch then there would be nothing left for us to find. It is estimated that if man left the Earth (or destroyed himself) today the only thing that would be discernible after a mere million years would be the Voyager craft still heading out.

Not saying that this did happen. Just cautioning against the view that civilization and intelligence only arose once on this planet.
ACW
5 / 5 (2) Jan 16, 2012
Using Earth as an example, despite several mass extinctions, life has resiliently continued here.
Taking into account the fact that life does not necessarily need to conform to what we are familiar with here on Earth, I feel that it is highly probable that life exists elsewhere in the universe.
ACW
4.3 / 5 (3) Jan 16, 2012
To add to my previous post: Considering that the Universe has been here for an estimated 13 billion years and our own sun a mere 4.5 billion, life could have had much more time to develop in other systems. IMHO, it just increases the odds.
Koen
3.5 / 5 (16) Jan 16, 2012
@Dogbert
All earth atmospheric oxygen was created by plant life during the evolution of life on earth. So, initially, atmospheric oxygen is not essential for life to evolve on a planet.
antialias_physorg
5 / 5 (6) Jan 16, 2012
onsidering that the Universe has been here for an estimated 13 billion years and our own sun a mere 4.5 billion, life could have had much more time to develop in other systems.

That's a bit of a problematic line of thought. The first generation of stars were all hydrogen and helium (and a smattering of Lithium).
The matter that could have formed planets at that time would have been of that kind, too. Heavier elements only came into being after the first generation of stars produced them through fusion and then were dispersed when these stars went (super) nova.

So there is a considerable time in the universe where life could not have come into being (unless there is some form of life that can be formed by hydrogen and helium alone - something that seems unlikly).

Though being fairly big (probably) the first set of stars would have had lifetimes which are mere millions of years instead of the billions the current crop have.
Osiris1
1 / 5 (4) Jan 16, 2012
This on certainly received a LOT of comments.
dogbert
1.3 / 5 (15) Jan 16, 2012
Koen,
@Dogbert

All earth atmospheric oxygen was created by plant life during the evolution of life on earth. So, initially, atmospheric oxygen is not essential for life to evolve on a planet.


I know that. My point too. The article talks about habitable planets. Planets in every important measurement to the earth but lacking life would not be habitable to human beings because there would be very little free oxygen.
Modernmystic
1 / 5 (8) Jan 16, 2012
Faith means unconditional belief, which includes belief absent of or even despite of evidence.


That is ONE meaning...

http://dictionary...se/faith
Deathclock
1.4 / 5 (9) Jan 16, 2012
Faith means unconditional belief, which includes belief absent of or even despite of evidence.


That is ONE meaning...

http://dictionary...se/faith


I've already explained why the dictionary definition of faith being belief without proof is useless... there is no such thing as "proof"... I'm not typing all of this again.
Modernmystic
1 / 5 (14) Jan 16, 2012
So, MM, since we can't really live in a world where nothing is more certain than anything else, how would you compare the certainty of the existence of an interventionist god (most common form of faith) and the newly discovered level of certainty that life exists on extrasolar planets?


I'm pretty certain of both, since I'm not afraid to have an opinion that's not peer reviewed, cross checked, and properly codified by pontificating intellectual blowhards...

Deathclock
1.3 / 5 (9) Jan 16, 2012
MM, any definition of faith that is synonymous with belief is useless to me, there is no reason to have two words that mean the same exact thing. Any definition of faith that refers to it as "belief without proof" is also synonymous with belief, because belief is also inherently without proof. There is no such thing as objective proof, only proof relative to a context which is defined by axioms, or initial assumptions.

The only definition of faith that does not make it a perfect synonym for belief is unconditional belief, or belief with, without, or in spite of the evidence. Belief, then, would be better described as rational belief, or belief based on or due to the evidence.

It may be easier to facilitate such a discussion by first agreeing do away with both words, and refer only to rational and irrational belief. Agreed?
ACW
4 / 5 (2) Jan 16, 2012
@antialias_physorg
However, the first supernovae occurred very quickly since extremely large stars tend to last a short time before becoming unstable--just the type of stars required for the distribution of heavier elements. (as you have pointed out)
So, the logic stands.

Skultch
5 / 5 (3) Jan 16, 2012
I'm pretty certain of both, since I'm not afraid to have an opinion that's not peer reviewed, cross checked, and properly codified by pontificating intellectual blowhards...


Ok. Then what specific evidence for an interventionist god do you have that allows for the same confidence level that this article's evidence claims for extrasolar life? All the "data" I have seen (sources used for the Torah, Bible, etc) has huge continuity problems. Treating this issue as if we were in a court of law, are any of those sources admissible? Or is your confidence derived in a different way?

(I hope my tone comes off as amicable.)
Modernmystic
1.2 / 5 (18) Jan 16, 2012
I hope my tone comes off as amicable.)


It does :)

In short I'm not going to debate the continuity of the Bible on this site. There are independent accounts and copies which point to both it's veracity and continuity (talking about the new testament). Moreover personal experience accounts for most of my confidence and conviction. Not at all how I derive my belief in extrasolar life.

I think that the principle of mediocrity is going to be severely challenged on this issue for SOME people however. My guess is that, as is it's way, the universe is going to surprise quite a few people. Especially those who are just sure complex life abounds everywhere...
Deathclock
1.8 / 5 (10) Jan 16, 2012
Moreover personal experience accounts for most of my confidence and conviction.


You really don't see the folly in that do you?
Modernmystic
1.1 / 5 (16) Jan 16, 2012
Moreover personal experience accounts for most of my confidence and conviction.


You really don't see the folly in that do you?


When you get a gut feeling about something you don't see the folly in ignoring it? Moreover, what you're saying is about you...not about me.

I think your position is perfectly reasonable and I respect it. If you don't respect my position that's fine. I do expect you to respect me as a person however...
TheGhostofOtto1923
2.2 / 5 (10) Jan 16, 2012
TheGhostofOtto1923,
Always have to interject religion into every discussion, don't you?

This discussion is about extrasolar life. It is not about religion.
Arf? You are being deceptive as your concept of faith is faith-based and the people here know it.

So when you mention faith it is with the implication that there is a creator to have faith in, who would be blessing us with ET neighbors if and only if he deemed fit.
In short I'm not going to debate the continuity of the Bible on this site.
-Because you usually lose badly.
There are independent accounts and copies which point to both it's veracity and continuity (talking about the new testament)
What do you guys mean by 'continuity'? Its veracity has been thoroughly disproved.
Moreover personal experience accounts for most of my confidence and conviction.
Personal experience colored by the need for someone to grant your wishes and give you immortality? Perception is so subjective sometimes yes?
Deathclock
1.4 / 5 (9) Jan 16, 2012
When you get a gut feeling about something you don't see the folly in ignoring it?


A "gut feeling" is simply a conclusion reached subconsciously or based on information obtained subconsciously. It is true that you see and hear far more than you are consciously aware of, particularly in terms of peripheral vision. This occurs quite frequently when people think they are being watched or observed. Do an experiment, next time you are riding as a passenger in a car on the highway look at each driver as they pass or as you pass them... 90% of them will turn and look back at you, even though you should be well outside of their cone of conscious vision when you are directly across from them or even a bit behind them.

Further, the human brain is a pattern finding machine. People see things in clouds and bowls of soup and toast grains all the time because that pattern finding ability is how we survived in the jungle, it allowed us to identify predators hiding in the brush.
Thrasymachus
1 / 5 (4) Jan 16, 2012
Unfortunately, Deathclock, and as much as I hate to appear to side with MM on matters of religion, the appeal to evidence as a way of distinguishing faith from more reasonable forms of belief just moves the goalposts. Nobody believes that any of their beliefs lack evidence. MM, with his appeal to his own personal (subjective) experience and "gut feelings" is attempting to give a reason for his belief, though it's a reason he acknowledges you (and most others) probably won't accept as evidence.

So then you have to answer the question of what counts as evidence, and this is a problem because the idea that x is evidence for/against y invokes the idea of relevance, that is, the connections and relationships between experiences/observations, and these are entirely subjective affairs. Inter-subjectivity is a pragmatic workaround to the problem, but fails to give a concrete definition to the concept of evidence. IOW, we can't tell what will count as evidence until everyone agrees.
Deathclock
1.8 / 5 (10) Jan 16, 2012
Yet we have formally defined what is and is not admissible as evidence in court proceedings... should that not serve as a sufficient framework?
Modernmystic
1 / 5 (6) Jan 16, 2012
Yet we have formally defined what is and is not admissible as evidence in court proceedings... should that not serve as a sufficient framework?


Short answer...no.
Deathclock
1.8 / 5 (10) Jan 16, 2012
Yet we have formally defined what is and is not admissible as evidence in court proceedings... should that not serve as a sufficient framework?


Short answer...no.


Is that because you have no evidence for your beliefs that would be admissible in a court of law?
antialias_physorg
4.1 / 5 (9) Jan 16, 2012
Eyewitness testimony is the lowest form of evidence (and has been shown to be more often wrong than not). In matters of belief we don't even have that. We have hand-me-downs of eyewitness testimony for a dozen generations until someone wrote something down. That sounds like a very, very bad form of evidence to me.

Gut-feeling is also more often wrong than not (any of you have ever had more than one relationship that didn't work out? Then your gut feeling is already worse than 50/50. I.e. you're better of guessing than trusting your gut feelings)

It is utterly astonishing how uncritical people are against their own gut feelings - and yet so critical against hard evidence that others can present.

'Personal' isn't the same as 'important' (or correct).
antialias_physorg
3.7 / 5 (6) Jan 16, 2012
However, the first supernovae occurred very quickly since extremely large stars tend to last a short time before becoming unstable--

Yes, but you have to add the time until the remnants of the supernova from the first stars coalesce again to form another solar system (sun AND planets). Most the shock front has to crash into another expanding cloud from another supernova because the stuff is heading outward at terrific speed and not likely to fall back upon itself.

Anyhow: The matter must coalesce again via gravity, And that takes time. A lot of time.
TheGhostofOtto1923
2.3 / 5 (9) Jan 16, 2012
Yet we have formally defined what is and is not admissible as evidence in court proceedings... should that not serve as a sufficient framework?


Short answer...no.


Is that because you have no evidence for your beliefs that would be admissible in a court of law?
Yah they already tried that and they lost badly
http://en.wikiped...es_Trial

-But of course they failed to learn from experience like the committed addicts that they are.
Skultch
3 / 5 (4) Jan 16, 2012
Moreover personal experience accounts for most of my confidence and conviction.


I respect that and do not see that as an unsupportable approach to life. I can also empathize with the desire to support that feeling with evidence, and then also be powerfully motivated to ignore/deny evidence to the contrary. I'm not saying it's logically valid in an argumentative sense, but I think it's valid from a life decision perspective. I'd like to see some of the more aggressive atheists out there try to handle, for a very long time, denying the gut feeling that their family loves them. That's just not a smart thing to do if you like yourself and want to be happy. What's more important in the long term: being *more* correct (logically vigorous), or being more happy? I realize the two are dynamically connected and that isn't a straight forward question. For me, I couldn't be happy knowing my opinion might be scientific or logically invalid. I don't assume others have the same desires.
Skultch
5 / 5 (2) Jan 16, 2012
Yet we have formally defined what is and is not admissible as evidence in court proceedings... should that not serve as a sufficient framework?


Short answer...no.


I'd like to know your long answer. To some, this issue can be more significant than any individual court case ever, yet you assert that this issue doesn't require even an equal amount of ...um...scrutiny? (not sure if that's the word I want there)
Thex1138
5 / 5 (1) Jan 16, 2012
Eventually scientists and astronomers will realize and conclude that galaxies are life giving ecosystems...
Thrasymachus
1.2 / 5 (5) Jan 17, 2012
Actually, there's not a single standard for what counts as evidence in a court of law. There are standards for the admissibility of evidence, but those have more to do with excluding things that would actually be evidence if they were allowed, but are excluded for procedural reasons. The admissibility of testimony and physical evidence, and the weight of its relevance, are determined jointly by the plaintiff/prosecutor, defendant, judge and/or jury through the use of precedent, argument and deliberation. In other words, the "standard" for the law for determining what counts as evidence is still just inter-subjective agreement, which still doesn't help us at all in figuring out definitively what it means for x to be evidence for y. As a practical matter, faith defined as "belief in spite of evidence" is merely "belief in spite of intersubjective agreement otherwise." In other words, faith is whatever someone else believes in that you (and others) think is stupid.
GDM
5 / 5 (1) Jan 17, 2012
Sorry Thrasymachus, you need to talk to a lawyer or better yet a judge. The rules/standards of evidence are well established, at least in the laws of the U.S. What you refer to as precedent (Res Judicata) is the influence of previous decisions as they may relate to the current issue at trial. Res Judicata is NOT evidence.
Thrasymachus
1 / 5 (4) Jan 17, 2012
I'll make the issue simpler. Let's say we have an objective principle for what makes something evidence for something else. We'll call this principle P. If we want to know if x is evidence for y, where x and y are possible objects of experience, then we have to establish whether P holds between x and y. Now, if your belief in P is rational, then you'll have reasons for believing in it, that is, there will be evidence for P. But P is the principle that establishes what it means to be evidence for something. So your evidence would read, "According to P, x is evidence for P." This is an illegitimate form of arguing known as begging the question.

What this implies is that there is no P. That is, there is no single, bounded principle that establishes what it means for x to be evidence for y. The nature of evidence is unconditioned itself, so distinguishing faith from supported belief by its un/conditioned relation to evidence won't fly.
TheGhostofOtto1923
2.2 / 5 (10) Jan 17, 2012
Actually, there's not a single standard for what counts as evidence in a court of law.
Actually there are various standards for what constitutes evidence in a court of law as GDM points out.
http://en.wikiped...of_proof
I'll make the issue simpler.
And from that statement you proceed to word calculating? How does that make anything 'simpler'? 'Blah plus blah equals blah' -? It never worked in philosophy and it doesnt work here. For instance
The nature of evidence is unconditioned
'Unconditional - without conditions or limitations...' Evidence always includes within its nature where it came from, how it was collected, how it pertains to the situation at hand, who collected it and for what reasons, etc. Your use of the synonym 'unconditioned' is not only ludicrous but pretentious, and even more so your fabrication un/conditioned. Is that crap meant to add weight to an empty argument? Obviously - thats how philos do things.
GDM
not rated yet Jan 18, 2012
All evidence must be based on "facts", which is where the "belief system" comes in. Only after mutually agreeing that a statement is factual, can it be considered. The fact must then be considered "relevant" to the argument being made, and must also be "material". Contradictory facts may also be admissible, leaving the jury (as the decider of the facts) to sort out. All of this is based on basic logic/deductive reasoning. The study of evidence is a minimum semester-long course in law school, so no discussion here will ever suffice. Bottom line: "Facts" are the foundation, and how we go about determining their validity is where belief and faith come into play. As to the relevance of these posts to this thread, when you start with the most basic "facts" (amino acids exist in space), eventually you must conclude that life is virtually everywhere in the universe (given certain conditions).
Seeker2
1.7 / 5 (7) Jan 21, 2012
dogbert,
You cannot rationally assign a positive probability when there are zero known instances outside this solar system.
I remember something from a previous life about Bayesian probability theory and what they call a maximum likelihood estimator. The idea goes something like this: We know intelligent life exists in this solar system (I think). Any other solar system we haven't a clue. Maybe yes, maybe no. So until you gather more information you have to assign equal probabilities to each possibility. So our best guesstimate is in 100 billion galaxies there will be 50 billion galaxies with intelligent life.
An assertion of certainty has no rationality.
True. Our best guesstimate is the chance we could be wrong is 1/2 to the power of 100 billion.
Seeker2
1 / 5 (5) Jan 21, 2012
Technically 1/2 to the power of (100 billion - 1)
antialias_physorg
5 / 5 (3) Jan 22, 2012
I remember something from a previous life about Bayesian probability theory

I think you better go hit the books on that one again.

As long as we have no information no probability can be assigned. This goes for bayesian (or any other kined of) probability measures.
Seeker2
1.4 / 5 (9) Jan 22, 2012
As long as we have no information no probability can be assigned. This goes for bayesian (or any other kined of) probability measures.
Sounds good but not exactly applicable. We know there are 2 possibilities. We have no information about which possibility might be more likely for other galaxies. Therefore fess up to your ignorance and don't just throw up your hands in despair. Make an unbiased guess until you get more info - yes 50%, no 50%. Sort of like heads or tails. I've been beating my drum for many years trying to get people to think.

Actually there are caveats. We're only considering the possibility that sometime in the galaxy's history there was intelligent life. Also we can be certain what you see is not what's actually going on now.
Seeker2
1 / 5 (4) Jan 30, 2012
It seems that comets are the incubators of life. Ideal environment - too hot, the ice melts off, too cold, the ice insulates the environment inside the head. Probably an ideal environment for the triple point of water.

A necessary condition for the formation of intelligent life may the the sun's corona which gets the attention of more intelligent bipeds, creatures who look up at the corona and begin to speculate. The speculators may inbreed leading to even more intelligent beings. Four-footed creatures who experience the darkness from the eclipses probably just figure it must be time to take a nap.

Anyway if the viewing the corona is a necessary condition for intelligent life to evolve, the sun-moon-earth geometry becomes critical. Possibly a 5% or even less variance from what we have may exclude the possibility of getting a good view of the corona.

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